Combustion flame in the combustion chamber of a turbine engine is facilitated by a series of pilot nozzles that supply fuel under pressure to the combustion chamber. Because they are exposed to the volatile environment of the combustion chamber (i.e. extreme heat, pressure and vibration), unprotected pilot nozzles can become warped or clogged and the fuel passing therethrough can coke, which can cause a dramatic decrease in the operational efficiency of the pilot nozzle as well as the combustion facilitated thereby. Inefficient combustion can lead to greater fuel consumption, a loss in the amount of power the turbine produces and/or an increase in nitrogen oxide emissions, all of which can significantly increase operating costs.
There have been many efforts directed to protecting the pilot nozzles from the harsh operational environment of a turbine engine. One general approach to protect pilot nozzles has included reducing the amount of heat to which pilot nozzles tips are subjected. For instance, water jackets or heat shields have been provided to protectively surround the pilot nozzle. The heat shields are generally cylindrical with a conical end. While such heat shields provide some degree of protection, a number of problems have been experienced with their use, including fuel flow obstruction and air flow obstruction.
Some heat shields have been reconfigured to minimize these problems. For instance, the conical end of the heat shield has been slotted to form a plurality of separated tangs, which can provide sufficient heat resistance. Such heat shields can result in extended part life and in the preservation of the intended functionality or performance. While an improvement over other prior heat shield designs, the generally cylindrical, tanged heat shields can suffer from a number of problems. For example, the tanged heat shields have a smooth inner peripheral surface. Thus, when cooling air is supplied in the space between the pilot nozzle and the surrounding inner peripheral surface, the flow of the cooling air remains substantially uninterrupted along the inner peripheral surface. Such uninterrupted flow can result in inadequate cooling under some operating conditions. Inadequate cooling can potentially lead to some of the same problems associated with prior heat shield designs, including a decrease in component life and engine performance. Thus, there is a need for a heat shield design that can minimize such concerns.